This invention relates to web processing of the kind in which the web is longitudinally compressed by driving the web at a nip line formed by pairs of spaced-apart, matched rotating disks and retarding the web by devices inserted in the groove spaced between the disks.
Devices of such disk drive type were suggested more than fifty years ago for making creped products which has more or less irregular, striped form. In Campbell U.S. 1,764,676, pairs of fingers, mounted upstream of the rolls, were shown to protrude into the grooves between the driving disks. The web driven between these fingers was said to fold upon itself alternately in opposite directions from a point of contact with one finger to that with another, and to subsequently pack into the space between the fingers before exiting from the machine. According to that patent, the fingers yieldingly moved or oscillated between a convergent relationship and a relationship in which the fingers were substantially parallel.
It is not known whether such a machine was ever employed commercially. In recent decades different disk drive approaches for longitudinally compressing a web have been used. Walton, U.S. Patent 2,915,109, and Packard, U.S. Patent 4,090,385, show longitudinally compacting a web by feeding it over a roll that has alternating, circumferential ribs and grooves along its length. A flat shoe presses the web against the roll to enable the ribs of the roll to drive the web forward. Then a cylindrical comb (rotating with a peripheral speed lower than the roll) or a fixed comb (whose teeth mate with the grooves of the main roll) lifts the web from the main roll and at the same time compacts it longitudinally. In the latter case, a wide, flexible metal sheet extension from the shoe engages the face of the web opposite the web face that engges the retarder comb, to form with the retarder comb a confining passage for the microcreped material. See also Walton U.S. patent 3,260,778.
Painter, U.S. Patent 3,390,218, shows pleating a web using one smooth roll and a second smaller diameter roll having alternating ridges and grooves. A third slower moving smooth retarder roll is held against the first smooth roll in a converging relationship to force the web back toward the nip, to cause pleating. In one example of this machine, a finger member, mounted upstream of the grooved roll, protrudes into the grooves to form one side of the longitudinal compression zone at the nip, preceeding the third roll.
In Cannard, U.S. Patent 1,680,203, a web is shown being creped by passing it into the nip between two drive rolls each having disks alternating with spacer elements. After passing through a relatively long confining passage, the web is engaged by slower rotating rolls which cause the web to crowd together to form the crepes in the long passage. The long passage is bounded by two sets of long, thin presser members, the forward ends of which are tapered and disposed in the spaces between the disks of the drive roll.
In a different type of machine that drives the web by a nip formed by two smooth rolls, two wide, curved blades mounted downstream in opposition to the nip have provided a retarding passage into which the web is forced and caused to compact, Walton et al., U.S. Patent 4,142,278.